Some duels or similar combats are meant to end when one of the participants causes the other to bleed or be otherwise injured. Whether or not this actually happens often depends on circumstances, but this is a stated stipulation or assumption of at least one participant.
- Blood Upgrade: A fight gets more serious once a combatant realizes they are bleeding.
- First Blood, when a combatant having blood drawn on them indicates that the fight is more serious than first thought.
- Single-Stroke Battle, where a swordfight ends with one participant killed by the other on their first swing.
Contrast Duel to the Death.
- In the 1930 storyline of Baccano!, Firo's knife fight with Maiza serves the role of a Gang Initiation Fight, with drawing first blood being the main rule. The other rule is that if you go for the kill, you'll be killed where you stand.
- At one point in Fullmetal Alchemist, Gori attacks Gluttony, declaring that the first to bleed is the first to fall.
- Played with in De Cape et de Crocs. While on the Moon, Armand is challenged to a local form of dueling called rixme, a portmanteau of rixe (brawl) and rime (rhyme) where the loser is the first to lose his flow. It's essentially an Enlightenment-era rap battle.
Armand: Until first blood?
Adynaton: Until the last word.
- The Many Sons of Winter: Domeric and Joffrey's duel is fought this way. The former wins by hitting the latter in the head and causing him to bite his tongue.
- The Mountain and the Wolf: Jaime is made to fight against a Slaaneshi champion until his real hand has been struck six times (he doesn't know it, but six is Slaanesh's sacred number), and this is repeated an untold number of times during his imprisonment. He finally maages to beat him after his golden hand is possessed by a daemon, making it able to move.
- The Pirate's Soldier: The Juraian noble Seiryo Tennan decides to challenge Heero to a honor duel, trying to revoke his birthright as a heir to the Juraian Empire. The only rules set up are that the first who draws blood from his opponent or forces him to surrender wins. Heero wins by headbutting Seiryo in the nose.
- Die Another Day: While James Bond and Gustav Graves are fencing at the Blades club, Bond proposes a bet over a diamond marked with the insignia of Graves's company (which also happens to be an African conflict diamond). Graves accepts, then takes a pair of decorative swords off the wall.
Graves: Since we're upping the wager, let's up the weapons, shall we? We'll do this the old-fashioned way, first blood drawn from the torso!
- An interesting exploitation of this trope happens in Rob Roy. At the very start of the film, Rob and company track down and capture a group of men who had stolen a herd of cattle from a Scottish lord, and Rob kills the leader in a duel. Later in the film, Will Guthrie, a friend of the leader of the thieves, comes up to Rob in an inn with his sword drawn, challenging Rob to a duel for revenge. Rob gets Guthrie to agree that the duel be to first blood only, then immediately reaches out, cuts his hand on Guthrie's drawn sword, and "congratulates" the other man on his victory. This handily (no pun intended) satisfies honor and leaves Guthrie no recourse for further revenge while also removing the chances of anyone dying in a duel, either via Rob accidentally killing Guthrie or Guthrie "accidentally" killing Rob by scoring a lethal first wound and then later pretending that he never intended to kill Rob.
- The Duellists:
- Feraud's first onscreen duel against a mayor's nephew is considered over after Feraud stabs the man through the chest, drawing blood and humiliating him, but it's later said that he will survive.
- Averted by Feraud and d'Hubert's subsequent many, many duels, which are often plenty bloody, but are always interrupted before they can finish each other off.
- In Dune, when Paul cuts Jamis during their duel, he asks if Jamis wishes to end the fight. This draws anger and disgust from the other Fremen until Jessica explains that Paul was trained to fight to first blood. He then learns that among the Fremen, such duels are to the death.
- In the Honor Harrington books, duels are legal in the Star Kingdom of Manticore and are governed by the code duello. Dueling under the Dreyfus Protocol limited each participant to five rounds which could only be exchanged in single shots, after which each party would be asked if honor was satisfied. The duel was automatically concluded at first blood, or if the participants ran out of ammunition. The bloodier Ellington Protocol allowed the duelists ten rounds each and had no limit on rate of fire, concluding only when one participant either dropped their gun in surrender or was dead.
- Exaggerated in The Man Who Was Thursday, when a duel that's meant as a distraction is stipulated to go to first serious injury to make sure the distraction lasts long enough.
- In the Warhammer 40,000 novel Chapter War, Eumenes challenges Sarpedon in the opening, with Sarpedon insisting on the fight being to first blood - something that allows Sarpedon to win even though he didn't land the first blow because Eumenes' strike hit Sarpedon's augmetic leg, which can't bleed. They fight again in the climax, this time to the death.
- Subverted in Reflections of Eterna (Winter Break), when Richard Oakdell challenges Valentine Pridd over a perceived insult and Valentine chooses to duel until first blood, but their respective seconds don't manage to stop the duel before both have wounded each other.
- In The Last Wish Geralt is challenged to a duel by an arrogant knight offended by the Witcher's presence in the kingdom. While the terms are to first blood, it's made very clear that the knight's brothers-in-arms will have Geralt's head if he dares to shed noble blood. So, Geralt parries the knight's sword with sufficient force that the idiot is cut by his own blade. It works because the judge didn't like the knights.
- In A Song of Ice and Fire, the first of many acts that would make Prince Oberyn Martell infamous was a duel to first blood. After a teenage Prince Oberyn was caught sleeping with the paramour of Lord Yronwood, the two agreed to have a duel to first blood, which would satisfy honor and let everyone move on without provoking a feud between the ruling family of Dorne and the powerful House Yronwood. Both Oberyn and Lord Yronwood were cut, but while Oberyn quickly recovered from his wound, Lord Yronwood's only got worse until he died. It was widely rumored afterward that Oberyn poisoned his blade, and it took a lot of diplomacy between Oberyn's older brother Prince Doran and the rest of House Yronwood to prevent any grudges from forming. While it's not confirmed in the books that Oberyn poisoned his weapon, the fact that he did do so in a different duel several decades later (albeit against someone he had much more cause to hate), hints that he might deserve the infamy he got as a result.
- Wednesday: Wednesday challenges Bianca, Nevermore Academy's Alpha Bitch, to a fencing duel to knock her down a peg. After they both win a round, Wednesday opts to have them both remove their facemasks and blade protectors and so the winner is decided by who draws blood first. Wednesday loses, much to her own shock.
- Some hardcore wrestling leagues have "first blood" matches, where the first wrestler that bleeds loses the match. TNA had a variant called Sadistic Madness, in which a wrestler couldn't be pinned until they had been made to bleed.
- In Legend of the Five Rings, iajutsu duels are a common way for rival bushi in Rokugan to settle differences, with first blood usually being the winning stipulation as the swordsmen's lives are too valuable to waste.
- In Battletech, the Clan Trial of Grievance is a personal honour duel between two Clanners. In all but the most high-profile cases, it will be to first blood (or ejection if the duel is done using Mecha) as duels to the death are considered wasteful and thus anathema to the Clans' way of life.
- The Dwarven Provings in Dragon Age: Origins are to first blood. Companion Oghren is banned from Provings or even carrying weapons in Orzammar due to accidentally killing an opponent.
- Solatorobo: On the Duel Ship, Red will occasionally find himself in a Self-Imposed Challenge where he declares that he'll win without taking a single hit, making it a duel to the first blood for his opponent, while Red still has to defeat them the normal way.
- Kill Six Billion Demons: Invoked by the immortal God-Emperor Solomon David, who offers one wish — up to and including his own throne — to anyone who can draw one drop of his blood in a public duel. Since he's Nigh-Invulnerable Person of Mass Destruction, none of the chancellors vying to become his heir are willing to try. At the end of the arc, the angel 82 White Chain manages to put a small bruise on his cheek. Even though she didn’t technically draw blood, the audience is so amazed and impressed that she injured him at all that Solomon David declares her the winner anyways, lest he lose face with his empire.
- Dominic Deegan: The climactic fight in the "Battle for Barthis" arc between Szark and Scarlatti is fought under these terms. Due to his pre-Heel–Face Turn habit of starting duels to the death in order to relieve the pain from his infernal Wound That Will Not Heal through murder, there's some concern that Szark won't be able to hold himself to these terms, but he ultimately manages to control himself and wins with a sudden I Am Not Left-Handed moment, and knocks the toupee off Scarlatti's patron with the same stroke.
- Heric from Xcalibur once had to fight in such a duel. Since he was not only a mage apprentice but also a Bare-Fisted Monk, all it took was a kick in the face.
- In Transformers Aligned Universe, this is why Megatron leads the forces of the Decepticons. He and Soundwave — his information officer — dueled for the leadership of the Decepticons during the faction's inception in a fight that was explicitly first to wound. Megatron himself has admitted that had the duel been to the death, Soundwave would have won, and Transformers: Prime makes it blindingly obvious that anyone thinking of overthrowing Megatron has second thoughts because even if Megatron is out of the way, Soundwave isn't, his loyalty to Megatron is undying as a result of the first-to-wound duel, and due to his role as information officer he likely already knows what they're planning.
- Holmgang duels between real-life Norsemen were often done like this when they weren't a Duel to the Death, especially in Iceland. From Kormák's saga:
Each contestant was to have three shields, and when they were destroyed then he must step on the cloak again if he had left it before, and defend himself with his weapons thereafter. He who had been challenged was to have the first blow. If one of the two was wounded so that blood flowed on the cloak, then no further fighting was to be done.
- The option for this is included in a number of dueling codes, in an attempt to keep the body counts down in societies where dueling is considered acceptable behavior. Of course, in fights with real weapons, it is entirely possible for the first blood to stem from a crippling or fatal injury.
- An increase in duels that use this trope is the reason for the design of the épée, eventually developing a three-pronged point that would gouge out a small chunk of flesh in a painful but rarely dangerous way before making the transition to an electronic scoring system. This is why modern épée fencing has no right-of-way rules and works purely on who hits first - unlike foil and sabre, which were derived from training for fights to the death and thus make defending against attacks a higher priority.